If your wrists are bare then it's harder to get your wrist broken or thrown, if your torso is bare then it's harder to land a bash against you, etc. The chances aren't super high that these skills that'll fail but I've had them work multiple times against an enemy in one fight. The short timer is handy because you can use normal armor most the time then remove a piece if it's a situation that it may come in handy for, ie vs orc or giant basher or an assassin, etc. If you're curious about some of these things, you can always ask someone to spar with you that can do these things.